Additive manufacturing in metals with a fiber array laser source and adaptive multi-beam shaping

ABSTRACT

A system for LAM that uses a scalable array of individually controllable laser beams that are generated by a fiber array system to process materials into an object using a powder bed, wire feed, or direct deposition. The adaptive control of individual beams may include beam power, focal spot width, centroid position, scanning orientation, amplitude and frequency, piston phase and polarization states of individual beams. These characteristics can be independently adjusted to control LAM characteristics including microstructure, mechanical and surface quality characteristics. The system may also have a set of material sensors that gather information on a material and environment immediately before, during, and immediately after processing. This information can be used to adapt the material processing routine to improve LAM productivity and parts quality. The system also supports a variety of beam shaping methods that improve the quality of produced objects or mitigate processing issues.

FIELD

The disclosed technology pertains to systems for metal additivemanufacturing using a multi-beam fiber array laser power source withadaptive shaping of spatiotemporal laser power distribution, and in situsensing systems.

BACKGROUND

Lasers are a common power source for material processing and metaladditive manufacturing, such as laser additive manufacturing (LAM)technologies. As one example, metal powder bed LAM involves amanufacturing platform or bed that can be raised and lowered during themanufacturing process. A thin layer of metal powder is evenly spreadacross the bed, and then a laser is used to heat the metal powder in adesired pattern so that it melts and then cools, while the unaffectedpowder material can be brushed away, leaving only the newly formedlayer. After each layer is formed by the laser, the powder platform islowered and a new layer of metal powder is spread on top of the oldlayer. In this manner, a three-dimensional object can be formed, onelayer at a time, by lowering the platform, adding a new powder layer,and then using the laser to melt the powder in the shape of a desiredobject volume into the new powder layer, where it then cools,consolidates into metal and bonds with the previous layer [1-4]. Themajor drawbacks of existing laser power sources for LAM are the lack ofactive and/or adaptive control of the laser beam spatiotemporalcharacteristics during laser energy deposition and lack of appropriatein situ sensing techniques for characterization of both stock materialin front of the processing beam and melted and consolidated into metalmaterials inside the processing beam and the heat affected zone (HAZ),during and after LAM processing of each layer. The lack of suchreal-time sensing techniques prevents development and implementation ofthe beam control techniques including, programmable, feedforward andfeedback control of LAM processes to improve productivity, repeatabilityand quality of LAM-built products and components [5].

It has also been found that the desired improvement of micro-structureand surface finish, mitigation of residual stress, and increase ofprocessing speed are difficult to achieve with a single laser beam. Theavailability of advanced power sources and control systems disclosedherein, capable of simultaneously projecting multiple laser beams whosecharacteristics, such as optical power, focal spot size, pointing andsteering characteristics, can be individually controlled, will createnew opportunities for LAM.

Recent technology developments may indicate a trend towards examiningthe advantages of, and developing systems for, multi-beam controllablelaser power sources for material processing and LAM. Currently, severaldual-beam and four-beam laser systems adapted for laser materialprocessing and LAM have been demonstrated [6-7]. The existing multi-beamLAM systems utilize separate optical trains for each beam composed oflaser sources (100.1) that generates laser beams (100.2), beam forming(100.3), scanning (100.4), and focusing (100.5) optics. FIG. 1illustrates a LAM system for independent processing of the stockmaterial using N projected beams (100.6) that form focal spots (100.7)at the powder bed surface (100.8) or other point of manufacture workpieces. Additional beam combining optics (100.9) are required to LAMprocessing with co-located or closely located focal spots as illustratedin FIG. 2 for the case of N-beam LAM. Scaling of the existing multi-beamLAM systems as shown in FIG. 1 and FIG. 2 to include large numbers ofindividually controlled laser beams would require the integration ofmultiple optical trains similar to those shown in FIG. 1 and FIG. 2,resulting in an extremely bulky, heavy and expensive LAM system. Inaddition, the demonstrated multi-beam LAM systems do not include sensorsfor feedback control and thus cannot provide on-the-fly modification oflaser beam characteristics based on work piece sensing data. The systemsand methods disclosed herein offer solution to these problems.

Another major drawback of the existing LAM systems is that they arelargely based on the so-called single-point-processing technique [5,9].In the systems illustrated in FIG. 1 and FIG. 2, sharply focusedprojected laser beams (100.6) create highly localized (point) heatsources that are rapidly rastered (scanned) with beam scanning optics(e.g., galvo mirrors) for selective laser melting (SLM) of a stockmaterial.

This single-point-processing LAM technique suffers from several majordrawbacks:

A. A highly localized (point) heat source that is generated by a sharplyfocused laser beam at a powder bed or other manufacturing work piece,creates large thermal gradients in the processing material. Scanning ofthis point-heat source produces an elongated molten pool, which at highscanning speeds breaks into disconnected balls due to Rayleighinstability [10,11]. Both large thermal gradients and these ballingeffects negatively impact surface roughness, cause residual stresses andcracking in LAM, and limit productivity. Note that attempts to increaseLAM productivity by using higher laser powers with faster scanningspeeds could make surface finish and residual stress even worse [12];

B. In single-point processing, the laser beam spot diameter, rangingfrom about fifty to hundreds of microns, only marginally exceeds thecharacteristic powder particle size (˜10-45 μm for Ti-6Al-4V alloy[13]). The result is a tiny processing volume, containing acomparatively small number of powder particles of different sizes withinthe volume. Since laser beam absorptivity and the material's temperaturerise is dependent on particle size, any variability of the stockmaterial inside the small processing volume leads to anisotropy in heatdissipation, variations in local temperature gradients, and strong fluidflows in the molten pool [14-16]—all major factors that directly impactthe quality of LAM-produced components; and

C. Processing with a single laser beam requires high-speed focal spotrastering (scanning) to avoid unacceptably long manufacturing times.This in turn results in extremely high heating rates leading todisruptions in the powder bed layer or material from evaporative flows,and from splatter due to evaporative recoil and jetting [5,16]. Highheating rates also make it difficult, or even impossible, to achievereal-time sensing and control of LAM process parameters.

These drawbacks for current single-point LAM technology can bealleviated with systems and methods disclosed herein.

The most recent attempt to move beyond conventional single-point SLM isimplementation of the additive manufacturing process known as Diode AreaMelting (DAM) [17]. DAM uses an array of low-power individuallyaddressable laser diode emitters for parallel stock material processingthrough the use of multiple laser spots. The DAM approach has severalprinciple problems that prevents its transitioning from the currentearly stage lab experiments to the LAM industry. The large and highlyasymmetric divergence of laser diodes results in elliptical poor-qualitybeams that are difficult to concentrate (focus) into a spot that hassufficient power density to cause the stock material to melt. Toincrease the power inside each individual laser spot, these diode stackarrays can in principle be combined. However, this multiplexing of lasersources complicates the focusing of these highly divergent beams evenmore [18]. In addition, the laser spot position on the powder bedsurface or material cannot be individually controlled. This leads to ahighly spatially non-uniform combined laser intensity with no ability toachieve adaptive spatiotemporal power shaping. The novel components,systems and methods disclosed herein offer solution to the problemsdiscussed above as well as other problems present in conventionalsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings and detailed description that follow are intended to bemerely illustrative and are not intended to limit the scope of theinvention as contemplated by the inventor.

FIG. 1 is a schematic illustration of a laser additive manufacturingsystem that uses two or more (N=2, 3, . . . ,) projected beams withindependent laser sources, beam forming, scanning and focusing optics toform focal spots at different regions of a powder bed or other workpiece material surface for simultaneous fabrication of several parts;

FIG. 2 is a schematic illustration of a laser additive manufacturingsystem that utilizes two or more (N=2, 3, . . . ,) beam combiningoptical systems to focus two or more (N=2, 3, . . . ,) projected beamsat a powder bed or other work piece material surface;

FIG. 3 is a notional schematic of an adaptive multi-beam fiber-arraylaser additive manufacturing system (AMBFA-LAM);

FIG. 4 is another notional schematic of an adaptive multi-beamfiber-array laser additive manufacturing system (AMBFA-LAM);

FIG. 5 is a notional schematic of multi-beam transmitter section view ofan exemplary fiber array transmitter with attached optical receiver andsensing module;

FIG. 6 is a front perspective view of an exemplary fiber array laserhead system composed of seven fiber-based laser transmitters andattached four sensing modules;

FIG. 7 is a notional schematic of an exemplary fiber-based lasertransmitter module;

FIG. 8 is a schematic block-diagram of an exemplary multi-channeloptical power amplifier (MOPA) fiber system with controllers;

FIG. 9 is a notional schematic of an exemplary AMBFA-LAM system having avirtual lens-based fiber array laser head;

FIG. 10 is a notional schematic of an exemplary assembly of multi-beamrastering system that utilizes a virtual lens-based laser head attachedto a gantry system having beam pointing mirrors and material sensingmodules for multi-beam focal spot pointing at a powder bed surface ormanufacture point;

FIG. 11 is a notional schematic of an exemplary beam rastering systemusing a fiber array laser head with collimated beams and a gantry systemwith attached beam pointing mirrors and focusing lens for multi-beamfocal spot pointing at a powder bed surface or manufacture point;

FIG. 12 is a notional schematic of an exemplary AMBFA-LAM systemassembly with material sensing modules;

FIG. 13 is a front perspective view of an exemplary virtual lens-basedfiber array laser head with material sensing modules;

FIG. 14 is a notional schematic of an exemplary material sensing modulecomprising a probe beam laser illuminator and an optical receiver;

FIG. 15 is a notional schematic of an exemplary probe beam lasertransceiver (PBLT) sensor;

FIG. 16 is a diagram view showing a variety of exemplary beam shapingmethods that an AMBFA-LAM device is capable of performing;

FIG. 17 is a visualization of experimental evidence of materialmicrostructure control using 7-beam AMBFA-LAM system that utilizes beamshaping methods of FIG. 16 showing distinct difference in materialmicrostructure between the results obtained with conventionalsingle-beam SLM processing method (left) and using multi-beam SLMprocessing (right);

FIG. 18 is a schematic block-diagram of an exemplary AMBFA-LAM devicethat utilizes incoherent multi-channel optical power amplifier (IMOPA)system with controllers for multi-beam adaptive shaping; and

FIG. 19 is a notional schematic of an exemplary adaptive beam shapingsystem having multi-beam control capabilities.

DETAILED DESCRIPTION

The inventor has conceived of novel technology that, for the purpose ofillustration, is disclosed herein as applied in the context of powderbed and other types of laser additive manufacturing (LAM) in metals alsoknown as selective laser melting (SLM), direct deposition, wire feed,and other similar procedures. While the disclosed applications of theinventor's technology satisfy a long-felt but unmet need in the art ofLAM in metals, it should be understood that the inventor's technology isnot limited to being implemented in the precise manners set forthherein, but could be implemented in other manners without undueexperimentation by those of ordinary skill in the art in light of thisdisclosure. Accordingly, the examples set forth herein should beunderstood as being illustrative only, and should not be treated aslimiting.

AMBFA-LAM System Configuration

The adaptive multi-beam fiber-array laser additive manufacturing systemdisclosed herein, which may be referred to as AMBFA-LAM, is illustratedin FIG. 3, and a variation in FIG. 4. The AMBFA-LAM system (300), whichmay also be referred to as a laser transmitter module, may beself-contained within a single case, chassis, or module, or may bespread across one or more cases, modules, or devices. The AMBFA-LAMsystem (300) is comprised of the multi-beam fiber array laser head(400), which may also be referred to as a laser transmitter ormulti-beam transmitter, that may have integrated beam pointing and/orfocusing modules, beam forming optics (100.5), one or more powder bedsensing modules (500), the multi-channel optical power amplifier (MOPA)fiber system with controllers (600), beam rastering controller (300.3),and a target object definition data (300.4), which may be generated byan additive manufacturing CAD software or another source, that providesparameters for an object to be fabricated, which may also be referred toas a target object. The AMBFA-LAM system generates multiplenear-diffraction-limited quality laser beams for simultaneouspre-heating, full melting and post-heating of the feedstock material onthe powder bed surface (100.8). In some implementations, the AMBFA-LAMsystem (300) may include integrated and/or attached passive(image-based) and active (probe lasers based) powder bed sensing modules(500) which may detect backscattered probe beam light (300.2).

While FIG. 3 shows a LAM system using a powder bed type point ofmanufacture, it should be understood that embodiments of the technologydisclosed herein may be utilized with points of manufacture other than apowder bed, and that some embodiments of this technology may rely upon awire feed point of manufacture, or direct deposition point ofmanufacture. A wire feed point of manufacturer uses a wire, coil, bar,or other form of solid material that is placed at the point ofmanufacture and then targeted by laser beams. As the material melts, newlengths of the wire or coil may be fed into the melt zone, and thematerials and lasers may be moved and adjusted as necessary to createthe desired object. A direct energy deposition point of manufacture usesa nozzle or other spraying mechanism to spray powdered material into themelt zone as needed. The deposition nozzle is often mounted proximatelyto the laser head, and the entire assembly may be positioned andoriented as needed to create the desired object. Each of these types ofmanufacture, powder bed, wire feed, and direct energy deposition, haveadvantages and disadvantages, and each may be used in embodiments of thetechnology disclosed herein as may be desirable based upon such factorsas desired cost, complexity, durability, environment and type of use.

While the technology described herein may use different point ofmanufacture types in different embodiments, for clarity, the figures anddescriptions will primarily depict and describe powder bed type systems.In a powder bed application, the processing beams transmitted by theAMBFA-LAM fiber array laser head and sensing probe beams move across thepowder bed surface using a beam rastering (scanning) system (100.4)based on galvo and or different type scanning mirrors, and/orhigh-precision x-y-positioning gantry platform. The target objectdefinition data is comprised of the coordinates for the multi-beamposition at the material surface, and a set of multiple beam parametersthat define spatiotemporal distribution of laser power at the material,which may also be referred to as a beam shaping method. In a timesequence of multi-beam rastering across the powder bed surface, a targetobject definition data is sent to the beam rastering controller (300.3).The beam rastering controller (300.3) supplies the multi-beam positioncoordinates to beam rastering system (100.4) that provides positioningof the configuration of beams at the powder bed surface based on thetarget object definition (300.4). A subset of the target objectdefinition data (300.0) that includes the set of multiple beamparameters defining the beam shaping method, are sent by the beamrastering controller (300.3) to the beam shaping controller (618) of theMOPA system (600) described below. The processing, receiving, andtransmitting of the target object definition may be performed by one ormore processors or devices, and may be performed by processors arrangedand configured in various, ways. Alternative implementations will beapparent to one of ordinary skill in the art in light of the disclosureherein. For example, in one implementation, the beam rasteringcontroller (300.3) and the beam shaping controller (618) could be thesame processor, controller, or device, so that part or all of the targetobject definition may be provided to different methods or functionsbeing executed on that single controller, which could then providecontrol signals to other devices.

Fiber Array Laser Head and Sensing Modules

In this section, we discuss the basic hardware that is used in thedisclosed AMBFA-LAM systems and methods for AM in metals with a fiberarray laser sources and adaptive multi-beam shaping. The disclosedselection of elements, modules and subsystems comprising the AMBFA-LAM,as well as their combination and functionalities are arranged andconfigured in novel ways to specifically address the needs for theadaptive beam shaping in LAM applications. As a result, the AMBFA-LAMdevice (300) includes a variety of innovative elements, modules,sub-systems and functionalities that are useful for metallic LAMapplications.

The AMBFA-LAM device (300) in FIGS. 3 and 4 can be assembled havingdifferent configurations for the fiber array laser transmitter (400),also referred to as fiber array laser head, and for multi-channeloptical power amplifier (MOPA) system with controllers (600). TheAMBFA-LAM device (300) may also include integrated powder bed ormaterial sensing modules (500), beam forming optics (100.5), and beamrastering (scanning) system (100.4). FIG. 5 shows a front perspectiveview of an exemplary fiber array transmitter device (400) with attachedsensing modules (500). The fiber-array laser head (400) is used totransmit a single or multiple laser beams (403.0) that are focused intoa processing region (200.2) at the powder bed surface (100.8) using thebeam forming optics (100.5). The focal spots of the transmitted beamsmay be rastered over the powder bed surface using a beam rastering(scanning) system (100.4). As discussed above, embodiments of thistechnology may use wire feed or direct deposition systems instead ofpowder bed, in which case a beam rastering system (100.4) may bereplaced or modified to move and orient a beam and wire or a beam andmaterial deposition nozzle.

The material sensing modules (500) are used for characterization of: (a)powder particles prior to LAM processing, (b) molten pool during LAMprocessing, and (c) consolidated into metal track immediately afterprocessing. These material sensing modules may also provide feedforwardand/or feedback control of characteristics for the projected onto powderbed surface laser beams, which can be used to improve LAM productivityand quality. The material sensing modules (500) can be integrated intothe fiber array laser head or be attached to it, as illustrated in FIG.5 and FIG. 6, or be a part of beam forming (100.5) or beam rastering(100.4) systems, or be used independently on these devices. The materialsensing modules (500) may comprise one or several imaging sensors(500.4), one or more probe laser illuminators (500.1), and othercomponents. The material sensing modules (500) may also utilizeidentical or different wavelengths, include one or more opticalreceivers (500.2), and one or more probe laser transceivers (500.3).

The fiber array laser head device (400) in FIG. 5 is shown as composedof a set of densely-packed fiber-based laser transmitters (400.3) thattransmit laser beams (beamlets) used for multi-beam selective lasermelting (SLM) in metallic LAM. The array of beamlets is also referred toas a combined beam [19]. The fiber-based laser transmitters (400.3) canbe integrated into one or more fiber array clusters (400.1) that areconstructed by using the one or more fiber-based laser transmitters, asshown in FIG. 5. While the embodiment of FIG. 5 shows a fiber arraytransmitter having three fiber array clusters (400.1) composed on sevendensely-packed fiber-based laser transmitters (400.3), also referred toas subapertures, with the precise number of subapertures and the numberof fiber array clusters being varied based upon such factors as price,desired size and capabilities of the device (400) and other factors.FIG. 6 additionally shows 3D view (410.0) of an exemplary fiber arraylaser head system (400) composed of a single fiber array cluster withseven densely-packed fiber-based laser transmitters. The fiber arraycluster (410.0) in FIG. 6 has four sensing modules (500) attached to it.

The embodiment of FIG. 7 shows an exemplary fiber-based lasertransmitter (FBLT) module (400.3). The integrated densely packed arrayof the FBLT modules form the fiber-array laser head (400) fortransmission of multiple beams (403.0). The FBLT module has integratedcapabilities for the transmitted beam (403.0) electronic pointing andsteering at the powder bed or other material surface. Additionalcapabilities may include the transmitted beam divergence control thatallows electronic control of width for the laser beam focal spot (100.9)at the powder bed or material. The disclosed methods and algorithms forcontrollable shaping of laser power spatial distribution at the powdermaterial for LAM, as described below, make use the FBLT modulecapabilities for the transmitted beam pointing, steering and focal spotwidth control.

The FBLT module may include one or more integrated sensors (403.9),(403.10), and (403.18), also referred to here as beam sensors (60), forreal-time measurements of the transmitted beam polarization, pistonphase and power. The output signals of polarization (403.11) and pistonphase (403.12) sensors can be utilized for stabilization (locking) ofpolarization states (polarization locking) and piston phases (phaselocking) of the transmitted by the fiber array laser head (400) multiplebeams using the corresponding controllers of the MOPA system (600) asdescribed below. The output signals (403.11), (403.12) and (403.19) areprovided to the MOPA (600). Polarization and phase locking capabilitiesare part of the disclosed techniques for spatiotemporal control ofmulti-beam intensity distribution for LAM. As shown in FIG. 3, the MOPAsystem (600) may also be configured to provide signals (618.1) from beamshaping controllers (618), and to receive signals from beam sensors(60), which may comprise one or more of phase (403.10), polarization(403.9), and power (403.18) sensors.

The FBLT module in FIG. 7 uses a beam forming optical system (403.1)composed of a single lens or several lenses and/or mirrors. This opticalsystem transforms the laser beam that is emitted from the tip of thedelivery fiber (403.3) into an output beamlet (403.0). An exemplary beamforming system (400.3) in FIG. 7 is composed of three lenses: small sizecollimating (403.15) and negative (403.14) lenses, and output beamforming lens (403.17). The optical energy entering the FBLT module inthe form of a single mode Gaussian-shape laser beam is delivered by theMOPA fiber system (600). To provide the capability of angular pointingand steering for the transmitted laser beam, the end piece of thedelivery optical fiber (403.2) with fiber tip (403.3) may be assembledinside a fiber-tip positioning module (403.4) that can provideelectronically controlled x- and y-displacements of the fiber tip indirections orthogonal to the laser beam propagation axis [20,21]. Thefiber tip displacement results in angular deviation of the transmittedlaser beam, and corresponding displacement of the focal spot footprint(100.9) at the powder bed or other material surface. The control of thefiber-tip x- and y-displacements is performed using electrical signals(403.5) that are generated by the controller (403.6) in response toinput signals (618.1) from the beam shaping controller (618) of the MOPAsystem (600).

Angular steering for the transmitted laser beam can be also implementedusing the disclosed lens-x/y positioning module (403.13) capable forcontrollable x- and y-high precision displacement of a small sizenegative lens (403.14)—a part of the beam forming optical system(403.1)—in directions orthogonal to laser beam propagation axis. Thelens x- and y-displacements results in the outgoing beam wavefront tipand tilts leading to angular deviation of the transmitted laser beampropagation direction. The lens x-y position control is performed byapplying electrical control signals (403.5) that are generated in thecontroller (403.6) using the input control signals (618.1) from the beamshaping controller (618) of the MOPA system (600). A portion of the beamwithin the beam tail area (403.8) is clipped by aperture of thebeam-forming optics and used for sensing of beam characteristics withthe beam sensors (60).

The FBLT module (400.3) in FIG. 7 may include additional capabilitiesfor transmitted beam divergence control, which in turn alters the sizeof the focal spots projected onto the powder bed or material surface.The beam divergence control can be implemented using the disclosed lensz-positioning module (403.16) capable for controllable displacement of asmall size lens (403.15) along laser beam propagation direction (alongoptical z-axis).

Multi-Channel Optical Power Amplifier (MOPA) Fiber System

Basic fiber-optics hardware with controllers, referred to herein as themulti-channel optical power amplifier (MOPA) fiber system, that is apart of the AMBFA-LAM device (300) is illustrated in FIGS. 3 and 4. TheMOPA system (600) is used for laser power delivery to the fiber arraylaser head (400) and adaptive beam shaping in the described applicationsof metallic LAM.

The schematic of an exemplary MOPA fiber system (600) is shown in FIG.8. The MOPA system (600) in FIG. 8 is shown as composed of the followingbasic modules:

A single mode narrow linewidth seed laser (601) with an optical modulethat provides laser beam coupling into a single mode polarizationmaintaining (PM) fiber (602).

The laser beam of the seed laser which is coupled into a single mode PMfiber, enters fiber splitters (606) that nearly equally divide the inputbeam between several (from 1 to N) single-mode PM fiber channels(606.1). The number of fiber channels (606.1) corresponds to the numberof beams that are transmitted by the fiber array beam laser head (400).Prior to splitting into fiber channels (606.1) the laser beam may beamplified by a fiber pre-amplifier (605) and, in some high-optical powerLAM applications, additionally phase modulated to increase linewidth andthus mitigate nonlinear effects in fibers [22]. The laser beam linewidthincrease (line broadening) is performed using a special line broadeningelectronic module (603) that supplies high (GHz-rate) random signal to afiber-integrated phase modulator (604) [23,24]. Note that in someimplementations line broadening may not be needed and if a broad lineseed laser (602) is used.

All fiber channels (606.1) of the MOPA fiber system (600) in FIG. 8 arecomposed of identical fiber-integrated components. For this reason, theembodiment of FIG. 8 shows only these fiber-integrated components for asingle fiber channel (606.2). After splitting into N channels in thefiber splitters (606), each laser beam passes through a controllablephase shifter (607), for example, lithium niobate (LiNbO₃) based [23].The phase shifters of the MOPA system introduce controllable variations(modulations) of optical path differences (OPDs) in the fiber channels(606.1). The controllable modulations of the OPDs are introduced by thepiston phase controller (615) and result in the corresponding changes ofthe aperture-average (piston) phases of the transmitted beamlets(403.0). Control voltages (617) applied to the phase shifters (607) aregenerated in a piston phase controller (615) using one or another beamshaping methods as described in further details below.

Related to the adaptive beam shaping method disclosed herein, thispiston phase controller may operate in the following regimes describedbelow: phase randomization (615.1), stair-mode beam steering (615.2),phase locking (615.3), and time-multiplexing control (616). Thetime-multiplexing control unit (616) is used to select and/or multiplexin time the operational regimes of the piston phase controller (615).

After passing phase shifters (607), the laser beams with modulated OPDsare amplified using the power fiber amplifiers (611) and throughdelivery fibers (403.2) enter the array of fiber-based lasertransmitters (FBLT) of the fiber array laser head assembly (400). TheFBLT modules (400.3) are described above and illustrated in FIG. 7.

In the beam shaping applications for LAM that require additional controlof the transmitted beams polarization states, the PM fibers are splicedwith non-PM delivery fibers as shown in FIG. 8 by the fiber splice point(608). Correspondingly, in this case, the power fiber amplifiers (611)may be also based on non-PM single mode fibers. In these applications,control of the transmitted beams polarization states is performed usingthe polarization controllers (610), which is configured to receivesignals (619.3) from the beam shaping controller (618). The controlsignals are applied to the polarization adjusters (609). Thepolarization controller (610) receives signals (403.11) from thepolarization sensors (403.9). These sensors could be either external inrespect to the fiber array laser system (400) or integrated into thefiber array system (400) as shown by (403.9) in FIG. 7.

Note that polarization control that results in identical polarizationstates for all transmitted by fiber array beams, also known aspolarization locking, is commonly required in high-power (kW-class)fiber array systems that intentionaly use non-PM fiber and fiberelements in the MOPA system in order to reduce non-linear effects infibers [22]. In the MOPA fiber systems based on PM single mode orlow-mode-number (LMN) PM fibers polarization locking may not berequired. In the LAM applications that may not require piston phase andpolarization control for beam shaping, the MOPA system (600) may bebased on, or include into it non-PM fibers and fiber components andsubsystems. In this MOPA system configuration, referred to as incoherentMOPA, the phase shifters (607) and polarization adjusters (609), as wellas the corresponding piston phase and polarization controllers andsensors are not required. The AMBFAL-LAM system (300) with theincoherent MOPA has reduced adaptive beam shaping capabilities that mayinclude the transmitted beamlets (403.0) electronic pointing, steeringand focal spot control at the powder bed or other material surface.

AMBFA-LAM Beam Forming and Rastering Systems

Implementing the described below configuration of the fiber array laserhead device (400), referred to here as virtual lens-based fiber arraylaser head, and selected laser melting (SLM) method referred to asremote SLM, the AMBFAL-LAM system (300) in FIG. 3 may be used withoutexternal beam forming optics (100.5), for example, without aconventional F-theta beam focusing lens [25], and/or withoutconventional beam rastering (104) system, for example based on galvoscatters [26]. This virtual lens-based fiber array laser head (401) isillustrated in FIG. 9. In this illustration, the fiber array laser head(401) of the AMBFA-LAM system generates an array of focused beams whosefocal spots are located at the powder bed or material surface positioneda pre-defined distance L from the laser head.

In the virtual lens-based fiber array laser head assembly (401), eachfiber-based laser transmitter (FBLT) module (400.3) shown in FIG. 7contains a beam forming optical system (403.1) that is designed to focusbeamlets at a distance L from the laser head. To overlap or position thebeam's focal spots in the processing region at the powder bed ormaterial surface, the fiber based laser transmitter modules (400.3) areassembled inside a specially designed mounting holder (400.1) atpre-calculated angles {α_(j)} (j=1, . . . , N) that are dependent on aselected distance L to the work piece, as illustrated in FIG. 9. Thevirtual lens-based fiber array laser head assembly (401) centers thebeams' focal spots inside a designated aim-point area of the workpiece—similar to what can be achieved with a large-aperture beam formingoptics (100.5) for example conventional or F-theta lens in front of thefiber array laser head (400) composed of fiber based transmitter modules(400.3) producing collimated output beams (403.0), as shown in FIG. 3and FIG. 6.

The distance L between the virtual lens-based fiber-array laser head(401) and the powder bed surface (100.8) can be specified based ontechnology-driven needs, and could significantly exceed the 20-50 cmupper limit of the currently used metallic 3D printing systems thatutilize conventional mirrors-based scanners, for examples scanners withgalvo-mirrors [26]. The possibility for significant (three-to-fivefolds) increase to the distance L between the laser head and the stockmaterial, which is achievable with the disclosed virtual lens-basedfiber-array laser head device (401), without causing an unacceptableenlargement in the combined laser beam focal spot size, and without needfor additional large aperture heavy and expensive beam forming optics,is highly desirable. Such extended-range (remote) LAM preventscontamination of the laser head and sensor optics by the heat and debristhat are generated in the heat affected zone (HAZ) at the powder bed ormaterial surface. Note that to keep the focal spot size unchanged withincreasing the beam focusing distance L, one may proportionally increaseoptical aperture size of the fiber array laser head and provide lockingof beamlet piston phases.

Having a longer distance L from the work piece additionally allowsreplacement of conventional mirrors-based beam rastering systems with ahigh-precision, high-speed x-y-gantry system (404.0) as illustrated inFIG. 9 and FIG. 10. FIG. 10 shows a beam rastering system using virtuallens-based fiber array laser head and x-y-gantry system (404.2). For thecombined beam rastering at the powder bed or material surface, thevirtual lens-based fiber array laser head (401) could be either directlyattached to the gantry platform (404.0) and move together with it asshown in FIG. 9, or be used to illuminate a simple assembly of beampointing mirrors attached to the x-y-gantry system as illustrated inFIG. 10, where the attached to the gantry system mirrors M₁ and M₂provide focal spot pointing to the powder bed surface (100.8). Themirror M₁ is attached to the movable platform (404.1) that moves inx-direction, while both M₁ and M₂ mirrors can be independently moved inorthogonal y-direction, thus providing beam rastering. Note that sincethe distance L between the laser head (401) and the powder bed (100.8)varies during beam rastering, the characteristic focal spot size d isalso changing. For long distance L and relatively small LAM workingenvelop, this undesired effect of focal spot size change is small.Otherwise, for large area LAM processing, the effect of focal spot sizechange can be mitigated using the corresponding controllable change ofthe focal distance of the fiber-based transmitters (400.3) with lensz-positioning modules (403.16) in FIG. 7. Another possible option isillustrated in FIG. 11, which shows a beam rastering system using fiberarray laser head with collimated beams and x-y-gantry system (404.5). Inthis multi-beam rastering method the fiber array laser head (400)generates collimated beams that are focused onto the powder bed ormaterial surface using the focusing lens (404.4). This lens is attachedto the moving x-direction platform (404.3) immediately after thepointing mirror M₁ and moves together with this mirror.

In summary, the disclosed systems and methods for remote multi-beamlaser power deposition into the powder bed or material surface with thevirtual lens-based fiber array laser head and x-y-gantry platform basedbeam rastering system allows: (a) elimination of conventional beamforming (100.5), e.g. F-theta lens, and beam rastering (100.4), e.g.,galvo-mirrors based systems, (b) increase the workspace envelope at thepoint of manufacture thus providing extra flexibility in LAM inmanufacturing larger parts, and (c) decrease in the laser-beam-inducedheat impact on both LAM-build parts and laser beam delivery optics.

AMBFA-LAM Material Sensing Systems

This section describes the disclosed here sensing methods and deviceswhich can be used either for in situ performance characterization of theLAM process, or for feedforward and feedback control of the multi-beamparameters and spatiotemporal intensity distribution at powder bedsurface or material surface, or for both. These sensing methods andsystems include:

(a) methods and systems for characterization of powder particles aheadof the LAM processing beam referred to here as powder particles sensing(PPS);

(b) methods and systems for sensing of consolidated into metal powdermaterial in the heat-affected zone behind the processing beam, referredto here as the processed-track sensing (PTS); and

(c) methods and systems for molten pool characterization, referred tohere as molten pool sensing (MPS).

The sensing methods disclosed are based on powder bed surface ormaterial surface active interrogation with probe laser beams for in situcharacterization of: (a) powder material ahead of the processing beam,(b) inside the processing region and (c) after material consolidationinto metallic processed track. Besides the probe laser-based sensing,the AMBFA-LAM material sensing capabilities may be enhanced by passiveimaging in visible, near-, middle-, and far-infrared spectral bands. Theschematic of FIG. 12 illustrates the material sensing modules including:the powder particles sensing (PPS) module (500.5), molten pool sensing(MPS) module (500.6) and the processed track sensing (PTS) module(500.7).

The AMBFA-LAM material sensors utilize one or more probe beam laserilluminators (500.1), and one or more optical receivers (500.2). Thesensors may operate at a wavelength that is identical or different fromthe processing beam (402.0).

Material sensing modules may be directly attached to either the fiberarray laser head (400) as illustrated in FIG. 12, or to the virtuallens-based fiber array laser head (401) in FIG. 9 and FIG. 13, or may beattached to a moving platform of the x-y-gantry system (404.1) asillustrated in FIG. 10 and FIG. 11, and thus move with the processingbeam (402.0) in a scanning direction (500.11) along the processing track(500.8), creating a molten pool (500.9) and leaving a consolidated intometal track (500.10) behind as the molten pool (500.9) cools, asillustrated in FIG. 12.

A notional schematic of a material sensing module composed of a probebeam laser illuminator (500.1) and optical receiver (500.2) isillustrated in FIG. 14. The probe beam laser illuminator (PBLI) andoptical receiver may be integrated into a single probe beam lasertransceiver (PBLT) device (520.3) illustrated in FIG. 15. The PBLTtransmits a probe laser beam (300.1) based upon one or more probe beamsignals (523.5) from a PBLI controller (523.6), and receives thebackscattered light (500.12). The disclosed sensors based on probe beamlaser transceivers are discussed below.

The schematic of an exemplary virtual lens-based fiber array laser head(401) with attached sensing modules is shown in FIG. 13. The sensingmodules include: powder particles sensor (500.5), processed-track sensor(501.0) and molten pool sensor (500.6). Both the powder particle sensor(PPS) and processed-track sensor (PTS) are based on probe beam lasertransceivers (520.3) illustrated in FIG. 15, while the molten poolsensor (MPS) includes both the optical (500.2) and the speckle-imagingreceiver (500.13) devices illustrated in FIG. 13 and FIG. 14 anddescribed below.

The schematic of FIG. 14 illustrates a material sensing module composedof the probe beam laser illuminator (500.1) and optical receiver(500.2). This material sensor may be used as a powder particles sensor(500.5), a molten pool sensor (500.6), a processed track sensor (500.7),or any combination thereof. Note that these material sensing modules maybe also based on the probe beam laser transceiver (520.3) illustrated inFIG. 15 and described below.

The optical schematic and functionalities of the PBLI device (500.1) inFIG. 14 are similar to the fiber-based laser transmitter (400.3)described above and depicted in FIG. 7. The PBLI device uses asingle-mode probe beam laser (523.15) that couples laser beam into asingle-mode fiber (523.2). The beam coupled into the fiber is deliveredto the fiber tip (403.3) that is installed inside a fiber-tipx-y-positioner module (403.4) described above. The PBLI beam formingsystem (523.1) provides a scaled in size image of the fiber-tip at thematerial surface, resulting in formation of a probe beam focal spot atthe manufacture material. The probe beam focal spot size may be, forexample, on the order of magnitude or smaller than the processing beamfocal spot. The fiber-tip positioner module (403.4) in the PBLI device(500.1) is used to: (a) center the probe beam focal spot alongprocessing beam track (along processing contour LAM-build part) with apre-set offset distance in respect to the processing beam focal spotand, (b) rapidly (several kHz speed) scan the probe beam focal spot in adirection orthogonal to the track line direction (501.1) as illustratedin FIG. 13. The offset distance between the focal spots of processingand probe beams, and scanning speed are set by the controller of thepowder bed sensors (620) shown in FIG. 14 and FIG. 8. The PBLI device(500.1) may include additional capability for controlling size of theprobe beam focal spot using the lens z-positioning module (403.16),similar the described fiber-based laser transmitter (FBLT) module inFIG. 7. The focal spot scanning may also be performed using a lensx/y-positioning module (523.13) also shown in both FIG. 14 and FIG. 7,and described above.

The material sensing module in FIG. 14 includes an optical receiver(500.2) composed of receiver optics (523.1), for example a lens, andphoto-detector (523.7). The optical receiver (500.2) that measures powerand other characteristics of the backscattered light (500.12) within thereceiver optics entrance aperture, is referred to here as thepower-in-the-bucket (PM) optical receiver. Another optical receivertype, that could be used in the powder bed sensing modules, is referredto here as speckle-imaging receiver (SIR). In the speckle-imaging typeoptical receiver, an imaging photo-array is used instead of thephoto-detector (523.7). The receiver optics (523.1) of the SIR typedevice is designed to provide a scaled image of backscattered specklefield at a selected distance L_(sp) between the material surface and theentrance aperture of the receiver optics (523.1). Note, that in the caseof the molten pool sensor (MPS) operating at the processing beamwavelength, the probe beam laser illuminator is not required. Opticalreceivers of such MPS devices, either PIB or SIR or both, usebackscattered light of the processing beam, as illustrated in FIG. 13 bythe molten-pool PIB (500.6) and speckle-imaging (500.13) receivers. Forbetter signal-to-noise ratio the optical receiver (500.2) may include abandpass filter (not shown) tuned to optical wavelength of the probebeam laser illuminator.

The probe beam laser transceiver (PBLT) sensor (520.3) disclosed hereand illustrated in FIG. 15, combines functions of the probe beam laserilluminator and the power-in-the-bucket receiver. The PBLT sensor(520.3) is based on a multi-core fiber (MCF) instead of a conventionalsingle-core fiber, as in the probe beam laser illuminator (500.1) inFIG. 14. The MCF has a central fiber core and one or several peripheralfiber cores. The tapered multicore-fiber connector (523.10) guides lightfrom each fiber core of individual fibers, referred to as receivedfibers (523.3). A probe laser beam is coupled into the center core ofthe MCF and after passing the PBLT beam forming optical system (523.1)creates a probe beam focal spot on the material surface. The lightscattered off the material surface propagates back to the PBLT sensoraperture. A portion of the backscattered light is coupled into the MCFperipheral cores and delivered to the photo-detector(s) (5.23.7) throughthe tapered multicore-fiber connector (523.10) and the received fibers(523.3). The photo-currents registered by the photo-detectors arecombined, and the corresponding signal (500.0) is delivered to the beamshaping controller (618) and/or the sensing data collection and analysismodule (530) of the MOPA system (600). The MOPA system (600) may alsoprovide one or more control signals (520.0) to the powder bed sensingmodules (500).

Methods of LAM Process Characterization and Control Based on MaterialSensing

In the material sensing methods disclosed, the focal spots of the probeand processing beams travel together with a constant offset distancebetween them. This allows real-time characterization of powderparticles, molten pool and the processed track throughout the entiremanufacturing process.

Analysis of the received signal from the PBLT sensor (520.3) that isused as the powder particles sensor (PPS) provides in situ informationabout stock material properties (e.g. powder particle absorbability,size distribution, and packing density) directly ahead of the processingbeam.

Similarly, analysis of the signal registered by the PBLT sensor (520.3)that is used as processed-track sensor (PTS) can be utilized tocharacterize the post-processed region.

Similarly, analysis of the signal registered by the PBLT sensor (520.3)that is used as molten pool sensor (MPS) can be utilized to characterizethe molten poll region. Note that the MPS device may operate withwavelength different from the processing beam. The output signals of thePBLT sensors can be utilized for feedforward control of the main beam.

In the material sensing method disclosed here, the PBLT sensor (520.3)may operate as a confocal microscope and provide live streaming imageryof a small region on the material surface along the processing track,ahead, inside and behind the processing beam. In the confocal imagingoperational regime, the probe beam focal spot is continuously scanningin a direction orthogonal to the processing part counter direction, asillustrated in FIG. 13. With a scanning speed significantly exceedingthe processing beam velocity, the PBLT can record a continuous stream ofline-scan images of the material surface ahead, inside, behind, or anycombination thereof, in relation to the processing beam.

LAM process characterization and adaptive beam shaping using thedisclosed method may be based on analysis of statistical characteristicsof the backscattered probe light. Statistical characteristics of theprobe beam light scattered off material surfaces depend onmicrostructure and roughness of the illuminated powder particles, onmolten pool surface properties, and on characteristics of the metallicsurface of the processed track. These backscattered lightcharacteristics, as measured by the material sensors, could be used forLAM process characterization and adaptive beam shaping.

Disclosed herein is a method for in situ characterization of materialsconsolidated into a metal track during LAM process using analysis of theprobe laser beam scattering off the material. The disclosed sensingmethod may also be used for the LAM process parameter optimization andfeedforward control. In this method for the processed trackcharacterization the appearance of balling defects in the consolidatedmetal is indicated by the presence of relatively low frequency and deepfluctuations in the received signal, while an increase in number of notfully melted, sintered powder particles and/or material porosity couldbe seen via a general decrease in the received signal average value.This, received from the material sensor data, can be utilized forfeedforward and feedback control and optimization of LAM parametersduring manufacturing process.

Also disclosed herein is a method for molten pool characterizationduring the powder bed metallic SLM with the described material sensors.Under ideal (desired) LAM processing conditions, the molten pool isspatially uniform (doesn't contain disconnected balls), occupies thelargest possible (for fixed total laser power) area inside the combinedmulti-beam footprint, and doesn't have evaporative flows and splatters.For these ideal conditions, the largest portion of power of thebackscattered probe laser light is reflected from the molten pool, whichbehaves as a mirror surface. For a probe beam slightly tilted withrespect to the axis that is orthogonal to the material surface, thelight reflected from the molten pool misses the PIB type opticalreceiver, resulting in a low PIB metric value. The appearance ofinhomogeneities inside this “perfect” molten pool, regardless of theircause (fluid flows, balling defects, splatter, etc.), will result in adecrease of the mirror-reflected backscatter light component andwide-angle light scattering off these inhomogeneities. This, in turn,will cause a corresponding increase in the registered PIB signal.Similarly, if the molten pool is too small and/or the beam footprint onthe material surface covers a significant portion of non-consolidatedinto metal powder or sintered particles, light scattering off theseparticles will result in a larger PM metric signal value.

These physics-based considerations suggest that minimization of theregistered PIB metric signal with feedback control of the beam shapingparameters described below could result in the formation of a smoothoptimally sized molten pool and thus high-quality LAM-produced parts.Note that due to the finite response time of metallurgical processes onthe control system-induced changes in the laser beam intensitydistribution, adaptive beam shaping may be based on minimization of thetime-averaged PM metric signal.

The molten pool formed during the described adaptive beam shapingprocess based on PM metric minimization may be consolidated into a shapethat is not optimal or even acceptable from the view point ofhigh-quality part manufacturing. Certain constraints on the controlparameters can be additionally imposed to keep the molten pool within adesired shape (e.g., a rectangle elongated along the processingdirection). These constraints may include limitations on the possibledeviation of the control parameters from the pre-selected values. Thus,monitoring of the PM signal of the molten pool sensor offers a methoddisclosed here for in situ the molten pool characterization andreal-time LAM process optimization via feedforward and/or feedbackcontrol of multi-beam intensity distribution.

AMBFA-LAM Capabilities and Methods for Spatiotemporal Beam Shaping

Capabilities of AMBFA-LAM device (300) for control of laser powerspatiotemporal distribution at the material surface—also referred to asbeam shaping—may include:

(a) Control of the projected to power bead surface, or other point ofmanufacture, beams powers {p_(j)} using the beam power controller (612),which is configured to receive either signals (403.19) from powersensors or/and signals (619.3) from the beam shaping controller (618),of the MOPA system in FIG. 8, where j=1, . . . , N and N is the numberof beams transmitted by the fiber array laser head (400);(b) Control of centroid coordinates {r_(j)}, of the focal spotfootprints (100.9) using either fiber tip x/y positioner (403.4), or/andthe lens x/y positioner (403.13) modules of the fiber based lasertransmitter (400.3) device in FIG. 7, and the beam shaping controller(618) of the MOPA system, where r_(j) is a 2D vector describing the jthfocal spot centroid location at the material surface;(c) Control of radii {a_(j)} of the focal spots (100.9) using the lensz-positioner (403.16) module integrated into the fiber based lasertransmitter (400.3);(d) Control of steering parameters of focal spots including steeringamplitudes {s_(j)}, angular direction vectors{θ_(j)}, and frequencies{ω_(j)}, using either fiber tip x/y positioner (403.4), or/and the lensx/y positioner (403.13) modules of the fiber based laser transmitter(400.3) device, and the beam shaping controller (618) of the MOPAsystem;(e) Control of polarization states of processing beams e.g. control ofangular vectors {m_(j)} of linearly polarized beams, using polarizationadjusters (609), signals from polarization sensors (403.11) andpolarization controller (610) of the MOPA system (600); and(f) Control of piston phases of the transmitted beams using the pistonphase controller (615), metric signal (614.1) and/or signal fromphoto-detector (916) and phase shifters (607) of the MOPA system (600).To simplify notations the set of control parameters that are used forbeam shaping are denoted here as {u_(m)}, where m=1, . . . , M, and M isthe total number of controls utilized for a particular beam shapingtask. Note that dependent on the AMBFA-LAM device (300) configurationand beam shaping needs the control capabilities may include all [(a)through (e)] the described above options, or be limited by a selectedset of them.

The disclosed beam shaping methods of the AMBFA-LAM device (300) areillustrated in FIG. 16. They include but are not limited by:

A. Incoherent combining with overlapping of all or several multiplebeams that could be achieved by controlling of the processing beamsfocal spot centroids {r_(j)}. This beam shaping method is illustrated bythe drawing (700.1) in FIG. 16;

B. Multi-beam phasing (also referred to as coherent combining) leadingto the reduction of focal spot size and corresponding increase of powerdensity at the work piece. Analysis has shown that phasing of N beams ofthe AMBFA-LAM laser source could result in an approximately N-foldincrease of focal spot peak intensity at the material surface [22]. Thedrawings (700.1) and (700.2) in FIG. 16 illustrate the processing beamfocal spots at the material surface with incoherent, also known asnon-phased (700.1), and coherent, also referred to as phased (700.2),combinations of seven beams. Note that multi-beam phasing results in theappearance of side-lobes located a distance from the processing beamcentral-lobe as shown in the drawing (700.2). These, located outsidemelting pool side-lobes can play the role of probe beams that could beused as probe beams for sensing of the material. The coherent combiningof beams could be achieved using output signals (403.13) of the phasesensors (403.12) that may be integrate into fiber-based transmittermodules (400.3) of fiber array laser head (400) as illustrated in FIG.7, or may be located along the optical train of transmitted laser beams(403.0), or both. The output signals of the phase sensors (403.12) areutilized by metric processor (614) that computes metric signal (614.1)characterizing deviations of piston phases from the desired phaselocking condition values. Using the metric signal, the phase lockingcontroller (615.3) computes the control signals (617) applied to thephase shifters (607) of the MOPA system (600) illustrated in FIG. 8. Thecontrol signals are generated via optimization of the metric signal(614.1) or signal (917) from photo-detector (916) that plays a role ofmetric signal, using one or another piston phase control algorithms,e.g. stochastic parallel gradient descent (SPGD) [27,28],multi-dithering [29], or LOCSET [30]. The exemplary piston phase sensingtechniques and multi-beam phasing control algorithms that may be used inthe MOPA system (600) are described in [31]. The multi-beam phasing maybe used for high resolution LAM processing of a component's contours toimprove surface finish;

C. Controllable randomization of the multi-beam piston phases resultingin improved laser power spatial uniformity inside the combined focalspot. Overlapping of the processing multi-beam focal spots (incoherentcombining) at the material surface may lead to random spatial andtemporal variations of the intensity caused by interference effects. Inthe disclosed multi-beam phase randomization method, these parasiticinterference effects of multi-beam LAM processing could be mitigatedusing fast (MHz- to GHz rate) randomization of piston phases of thetransmitted by the fiber array laser head (400) beams (403.0). Thepiston phase randomization is performed using the phase randomizationcontroller (615.1) of the MOPA system illustrated in FIG. 8, whichgenerates rapidly updating sequences of random piston phases. The pistonphase randomization leads to mitigation of interference effects andcorresponding improvement of spatial uniformity of laser energydeposition on the work piece. This AMBFA-LAM system with piston phaserandomization operational regime is illustrated by the drawing (700.3)in FIG. 16. The beam shaping using randomization of piston phases ofmulti-beams could reduce cooling and heating rate and improve quality ofLAM-produced parts or components;

D. Control of spatial distribution of the laser power density atmaterial surface using stair-mode beam scanning technique. The focalspot of the coherently combined beam can be scanned at high (tens ofMHz) speed by synchronous control of piston phases in the stair-modeoperational regime [32]. The disclosed stair-mode beam shaping methodfor LAM could be implemented using the stair-mode beam steeringcontroller (615.2) of the MOPA system (600). In the LAM applications,the stair-mode electronic beam scanning could, for example, be used forthe generation of an enlarged square-shape focal spot with a nearlyuniform intensity distribution. This beam shaping method using 2Dstair-mode beam scanning is illustrated by drawing (700.4) in FIG. 16.The stair-mode beam shaping may be used to control heating and coolingrate resulting in microstructure and material mechanical propertiesmodification, improve the surface finish for additive manufacturingproducts;

E. Superposition of highly localized beam for material melting and widebeam for surface treatment using the disclosed time-multiplexing beamshaping method that provides fast (>100 kHz) switching between coherentand incoherent beam combining operational regimes. The time-multiplexingresults in fast oscillation of focal spots corresponding to incoherentand coherent beam combining. On the time scale typical for LAMmetallurgical transformations, this time-multiplexing of laser beamintensity distribution produces the same result as simultaneous laserenergy deposition using two beams with different focal spot diameters.The coherently combined (smaller diameter) beam (701.2) can be used formolten pool formation, while the second (larger diameter) beam (701.1)can be utilized for the powder particles pre-heat and for slowingcooling process of the molten pool consolidation into metal. Bycontrolling the time duration of coherent and incoherent beam combining,any desired ratio of laser power can be distributed between theprocessing (melting) beam and the beam power used for surface treatmentin vicinity of the melting pool. This beam shaping method is illustratedby the drawing (700.5) in FIG. 16. The time-multiplexing laser powerdeposition beam shaping method can be also applied to otherspatiotemporal multi-beam control operational regimes. The drawing(700.6) in FIG. 16 illustrates intensity distribution obtained via timemultiplexing between vertical line scanning of one or more overlappingbeams and the stair-mode 2D scanning of other beams.

F. Powder material melting with simultaneous pre-heat of the powderparticles and annealing of the consolidated into metal material can beachieved by the disclosed beam shaping method of controlling multi-beamfocal spot centroid coordinates {r_(j)}, and/or radii {a_(j)}, and/orpowers {p_(j)}, and/or beams steering parameters {s_(j)}, {θ_(j)}, and{ω_(j)}. The drawings (700.7), (700.8) and (700.9) in FIG. 16 giveexamples of this beam shaping method including: (a) multiple beams intriangle shape (700.7) for pre-heating, and cooling rate control; (b)the multiple beams in line (700.8) for faster LAM processing andproductivity increase and for control of cooling and heating rate; (c)the ramp-shape intensity distribution illustrated by the drawings(700.9) and (701). This shape of beam can be obtained using various beamshaping techniques disclosed, e.g. by scanning of multiple beams withtheir partial overlapping. In ramp-shape beam gradual intensity increaseis used for pre-heating, high uniform power density for melting, andgradual intensity decrease for molten pool cooling.

The disclosed beam shaping methods leading to powder material meltingwith simultaneous pre-heat of the powder particles and/or annealing ofthe consolidated into metal material could be utilized for control ofthe material micro-structure and can be used for engineering ofLAM-produced parts with space-varying material micro-structure andmechanical properties. The experimental evidence of distinct differencein controlling the growth of gamma grain of IN718 alloy on the baseplate (800.3) with SLM processing of powder material using the disclosedmethods of beam shaping is illustrated in FIG. 17. The electronbackscatter diffraction (EBSD) inverse pole figure (IPF) maps (800)obtained with scanning electron microscope show radically different thecolumnar microstructure in two samples, one (800.1) processed usingconventional SLM method and the second (800.2) using beam shaping withseven beams in square shape. Note the small equiaxed grains in the IPFmap (800.2) compared to the very large gamma-type grain structure of thedeposited material (800.4) on the IN718 baseplate (800.3) in the IPF map(800.1).

The results in FIG. 17 were obtained using an exemplary prototype of thedisclosed AMBFA-LAM device (300) as the laser source.

Reduced number of the described beam shaping methods could beimplemented using a simplified option for the MOPA system (600) in FIG.8. This, referred to as incoherent MOPA (IMOPA) system (900), isillustrated by FIG. 18. The IMOPA utilizes independent fiber channelscomprised of either fiber coupled lasers (901), or with the fiber laserswith additional fiber amplifiers (611). Control of the transmittedmulti-beam powers could be performed either applying the power controlsignals (902) to the fiber coupled lasers or to the fiber amplifiers.The beam shaping controllers of the IMOPA systems (except piston phaseand polarization controllers) in FIG. 18 are identical to the describedcontrollers of the MOPA system in FIG. 8.

Algorithms of Spatiotemporal Control of the Multi-Beam Laser PowerDistribution for LAM

Also disclosed herein are exemplary control algorithms that could beapplied for spatiotemporal control of multi-beam laser powerdistribution using the AMBFA-LAM system (300). With a AMBFA-LAM lasersource generating N mutually incoherent Gaussian beams, thespatiotemporal intensity distribution of the combined beam at thematerial surface can be described by the function shown in Table 1,which is dependent on the described above 3N control parameters({r_(j)}, {p_(j)} and {a_(j)}).

TABLE 1 Spatiotemporal intensity distribution function${I\left( {r,t} \right)} = {\sum\limits_{j = 1}^{N}\;{{p_{j}(t)}{{\exp\left\lbrack {{- {{r - {r_{j}(t)}}}^{2}}/{a_{j}^{2}(t)}} \right\rbrack}.}}}$

Consider the following disclosed here beam shaping approaches:

Programmable Beam Shaping Using Error Metric Minimization.

Programmable control could be used to compute the multi-beam parameters{r_(j)}, {p_(j)} and {a_(j)} that provide optimal approximation of thedesired (reference) intensity distribution I_(ref) (r). This referenceintensity distribution could be selected using analysis and/or physicsbased considerations. In the disclosed programmable beam shapingalgorithm, the optimal control parameters and the best approximation forthe reference intensity distribution can be obtained via minimization ofthe error metric of Table 2, where integration is performed over thematerial surface plane. Minimization of the error metric of Table 2could be performed under a set of physics-based conditions andconstraints for metallurgical processes, such as the acceptable range oftemperature gradients inside the processing volume, power density levelrequired to melt powder particles of certain sizes, the combined beamrastering speed, etc.

TABLE 2 Error metric used for computation of optimal approximation forreference intensity distribution using beam-shaping control parametersJ(r₁, . . . ,r_(N),p₁, . . . ,p_(N),a₁, . . . ,a_(N)) = ∫∫[I(r) −I_(ref)(r)]²d²r

In the disclosed algorithm the programmable beam shaping is based on theStochastic Parallel Gradient Descent (SPGD) optimization [27, 27]. Tosimplify notation, the control parameters {r_(j)}={x_(j), y_(j)},{a_(j)} and {p_(j)} (j=1, . . . , N) are denoted as {u_(m)} (m=1, . . ., 4N), where u_(j)=x_(j), u_(j+N)=y_(j), u_(j+2N)=a_(j) andu_(j+3N)=p_(j). Using this notation, the focal-plane intensitydistribution is a function of 4N control parameters I(r)=I(r; u₁, . . ., u_(4N). The optimal values for these parameters are defined via aniterative process of the SPGD error metric minimization of Table 2,where u_(m) ^((n)), γ^((n))=γ(J^((n))), δJ^((n)), and N_(SPGD) are thecontrols, the gain factor, the error metric variation at the nthiteration, and the number of SPGD iterations, respectively. The errormetric variation δJ^((n)) in Table 3 results from small amplitude randomperturbations {δu_(m) ^((n))}=α^((n)){ζ_(m) ^((n))} of the controlparameters {u_(m) ^((n))}, where {ζ_(m) ^((n))} are random numbershaving a uniform probability distribution inside the interval [−1,1],and α^((n))=α(J^((n)))<<1 is the perturbation amplitude. To accelerateiterative process convergence, the SPGD control algorithm versiondescribed in Ref. [33] can be used, with adaptively changing gain andperturbation amplitude. With appropriately chosen parameters in theequation of Table 3, the SPGD iterations lead to error metricminimization and the corresponding optimal approximation of the desired(reference) intensity distribution I_(ref)(r).

TABLE 3 SPGD iterative algorithm for control parameters update u_(m)^((n+1)) = u_(m) ^((n)) + γ^((n))δJ^((n))δu_(m) ^((n)), m = 1, . . . ,4N_(SPGD) ,

Adaptive Beam Shaping Control Systems.

One of the major potential issues with programmable beam shaping is thatit requires the laser system and SLM process parameters to be exactlyknown and fixed in time. Under actual LAM conditions, there are alwaysuncertainties and variabilities in the stock material characteristics,shape and power of the transmitted beams, errors in beams pointing, etc.The beam shaping control (618) in FIG. 8, is comprised of feedforward(618.1A), feedback (618.1B) and programmable (618C) control systems,disclosed herein can account for these uncertainties via real-timeadaptive beam shaping parameters adjustment. A schematic diagram of theadaptive beam shaping systems that utilize the multi-beam controlcapabilities (e.g., A-F as described above with reference to FIG. 16) ofthe AMBFA-LAM device (300) are illustrated in FIG. 8, FIG. 18 and FIG.19.

In the adaptive beam shaping system (914) in FIG. 19 a beam splitter(910.1) redirects a small portion of the processing laser beam (402.0)power to an optical image forming system (911), e.g. a lens, thatcreates a scaled copy of the laser beam focal spot (100.7) intensitydistribution at the photo-array (913), referred to as a conjugate imageof focal spot (912). The photo-array is capturing the conjugate imagesof intensity αI(βr, t_(n)) at sequence of time {t_(n)}, (n=1, . . . )with a time interval Δt. The captured image αI(βr, t_(n)) represents ascaled copy of the intensity distribution I(r, t_(n)) at the materialsurface, where α and β are pre-defined and known scaling factors. Thecaptured images {αI(βr, t_(n))} are digitized and the correspondingsignals (918) are sent to the beam shaping controller (618) of the MOPAsystem (600). Using available data including the captured images {αI(βr,t_(n))}, scaling factors α and β, and the desired (reference) intensitydistribution function I_(ref)(r), the beam shaping controller (618)computes the error metric of Table 2. The same controller (618)iteratively updates the beam shaping control parameters, e.g.{r_(j)}={x_(j), y_(j)}, {a_(j)} and {p_(j)} (j=1, . . . , N) to minimizethe error metric of Table 2. The beam shaping control parameters updateis performed using one or another optimization algorithm, e.g. the SPGDoptimization algorithm of Table 3.

An additional sensing module in FIG. 19 that is composed of the beamsplitter (910.1), mask with pin-hole (915) and photo-detector (916)could be used for practical implementation of the described above beamshaping methods (e.g., B through E, as described above with reference toFIG. 16): Multi-beam phasing (B); Controllable randomization of themulti-beam piston phases (C); Control of spatial distribution usingstair-mode beam scanning technique (D); Switching between coherent andincoherent beam combining operational regimes referred to astime-multiplexing beam shaping method (E). To implement these beamshaping methods the signal from the photo-detector (917) is sent to thepiston phase controller (615) of the MOPA system (600). Maximization ofthis signal using a phase locking algorithm, SPGD for example, wouldresult in phasing (coherent combining) of transmitted by the fiber arraylaser head (400) beams at the photo-detector (916) and hence at thepowder bed surface (100.8) or other material surface. The same signal(917) can be used to maintain coherent combining of multiple beams atthe material surface with additional stair-mode beam steering signalsapplied to the phase shifters (607). The time-multiplexing controller(616) provides switching between coherent combining, incoherentcombining and controllable randomization of the piston phases thusimplementing the described above beam shaping methods (e.g., B throughE).

Additional beam shaping opportunities include utilization of signals(500.0) from the material sensing modules (500) described above.

Exemplary Systems and Methods

Discussed below are some but not all the innovations and features ofAMBFA-LAM (300) hardware and system disclosed herein.

AMBFA-LAM system architecture that provide capabilities forprogrammable, feedforward and feedback control of multi-beam laser powerspatiotemporal distribution, referred to herein as beam shaping, at thematerial surface for LAM.

Lens-positioner module that allows for control of widths of focal spotsat the material.

Fiber-based laser transmitter module with integrated capabilities forelectronic control of each or several or all of the following parametersof the transmitted laser beam focal spot: width, centroid location(pointing coordinates), steering frequency, angle and amplitude. Controlover these multi-beam characteristics provides capabilities that may beutilized for adaptive spatiotemporal control (shaping) of the laserpower distribution at the metallic material during LAM processing.

Fiber-based laser transceiver module with integrated capabilities forelectronic control of each or several or all parameters of thetransmitted laser beam focal spot and additional capability forsimultaneous sensing of each or several or all of the followingparameters of the transmitted laser beam: power, piston phase andpolarization.

Material sensors based on a probe laser- and power-in-the-bucket (PIB)receiver referred to here as the PL-PIB sensors, used for in situcharacterization of: (a) powder material ahead of the LAM processingbeam (powder material PL-PIB sensor); (b) molten pool inside the LAMprocessing region (molten-pool PL-PIB sensor); and (c) consolidated intometal LAM processed track (processed-track PL-PIB sensor).

Material sensor based on probe beam laser transceiver and referred tohere as the PBLT sensor that combines functions of the probe beam laserilluminator and the power-in-the-bucket receiver.

The above described AMBFA-LAM (300) system allows for a variety of novelmethods and processes, which include:

Methods for multi-beam selective laser melting (SLM) in metals based onadaptive fiber array laser technology with spatiotemporal control of thelaser power distribution.

A virtual-lens method for remote SLM with AMBFA-LAM.

Methods for control of multi-beam power distribution for SLM, including:(a) programmable control, (b) feedforward control, and (c) feedback(adaptive) control.

Methods for in situ sensing for LAM based on analysis of probe and/orprocessing laser beams to be used for feedforward and feedback controlof the multi-beam parameters and spatiotemporal intensity distribution,including: (a) methods for sensing of powder material ahead of the LAMprocessing beam; (b) methods for sensing of consolidated into metalpowder material in the heat-affected zone behind the processing beam,and (c) methods for sensing of molten pool.

Material sensing method based on the PBLT sensor operating as a confocalmicroscope providing live streaming imagery of a small region on thematerial surface along the processing track, ahead, inside and behindthe processing beam.

Methods for metallic powder or other material LAM processing including:

LAM processing with phasing of multi-beams (also referred to as coherentcombining) leading to the reduction of focal spot size and correspondingincrease of laser power density at the work piece—effective techniquefor high-resolution processing of contours of LAM-built parts orcomponents.

LAM processing with controllable randomization of the multi-beam phasesresulting in suppression of interference effects and improved laserpower spatial uniformity inside a designated processing area for LAM.

LAM processing with stair-mode scanning of the coherently combined beamsfor spatially uniform power distribution within an elongated (line) beamfor high-resolution part contour processing, and/or within rectangularshape regions for processing of a part's bulk material regions.

LAM processing with time-multiplexing between multi-beams phasing andphase randomization for simultaneous powder material preheat, meltingand treatment of the consolidated into metal material to improveLAM-produced parts quality (e.g., improve surface finish, reduceresidual stress, reduce risk of delamination, and other improvements).

LAM processing with multi-beam intensity patterns enabling optimalcontrol of heating and cooling rates, and an increase of processingspeed via controllable displacements or/and periodic oscillation of thefocal spot position of each beam in the extended vicinity of the meltingpool.

LAM processing with adaptive compensation of heat-induced phaseaberrations caused by heated air flows near material surface processingarea which may result in spatiotemporal fluctuations of laser powerdistribution inside the processing region and its vicinity, which maynegatively impact the surface finish of deposited material.

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The invention claimed is:
 1. An additive manufacturing systemcomprising: a manufacturing surface comprising a material and a targetobject; a laser transmitter module operable to produce a set of laserbeams to heat the material, comprising: a fiber array laser headcomprising a set of fiber-based laser transmitters, and a multi-channeloptical power amplifier system comprising one or more controllers, themulti-channel optical power amplifier system operable to provide laserpower to each of the set of fiber-based laser transmitters, and toprovide control signals to generate and modify spatiotemporal laserpower distribution formed by the set of laser beams at the material; abeam rastering system operable to position the set of laser beamsrelative to the target object; a beam rastering controller, wherein thebeam rastering controller is communicatively coupled with the lasertransmitter module and the beam rastering system; wherein the beamrastering controller is configured to: receive a target objectdefinition, the target object definition comprising a set of coordinatesdefining the target object, wherein a beam shaping method selected froma set of beam shaping methods is associated with each coordinate of theset of coordinates; determine a preconfigured instruction set based uponthe target object definition and provide a first portion of thepreconfigured instruction set to the laser transmitter module and asecond portion of the preconfigured instruction set to the beamrastering system; and based on the preconfigured instruction set and forat least one coordinate of the set of coordinates, cause the beamrastering system to position the set of laser beams and cause the lasertransmitter module to perform the beam shaping method.
 2. The additivemanufacturing system of claim 1, wherein the laser transmitter modulefurther comprises: a set of sensors comprising one or more of: a set ofbeam sensing modules, and a set of material sensing modules; and a setof beam forming optics operable to modify one or more of the set oflaser beams, characterization of the material, and control of anadditive manufacturing process based upon the output of the set ofsensors; wherein the one or more controllers are configured to: receivea set of sensor data from the set of sensors; determine a dynamicinstruction set based upon the target object definition and the set ofsensor data, the dynamic instruction set comprising a dynamicinstruction set for a beam shaping method that is selected to improvethe manufacturing process and quality of the target object; and providea first portion of the dynamic instruction set to the beam rasteringcontroller; wherein the dynamic instruction set is configured, for atleast one coordinate of the set of coordinates, to guide the beamrastering system to position the set of laser beams and cause a dynamicbeam shaping method to be performed based upon the dynamic instructionsset for a beam shaping method.
 3. The additive manufacturing system ofclaim 2, wherein the set of material sensing modules comprises one ormore of: a manufacturing surface sensor comprising a first probe beamlaser illuminator and a first optical receiver, configured to provide afirst probe beam oriented and focused to precede a path of the set ofbeams and operable to determine characteristics of a powder materialprior to a molten pool stage along a processing track; a molten poolsensor comprising a second probe beam laser illuminator and a secondoptical receiver, configured to provide a second probe beam oriented andfocused at the molten pool area and operable to determinecharacteristics of a molten pool; and a processed track sensorcomprising a third probe beam laser illuminator and a third opticalreceiver, configured to provide a third probe beam oriented and focusedto follow a path of the set of laser beams behind of the molten pool andoperable to determine characteristics of a processed track.
 4. Theadditive manufacturing system of claim 1, wherein the manufacturingsurface is selected from the group consisting of: a powder bed table; awire feed table; and a direct energy deposition table.
 5. The additivemanufacturing system of claim 1, wherein the one or more controllers areoperable to control the characteristics of a set of laser beam focalspots, at the material surface, of the set of laser beams produced bythe laser transmitter module, the characteristics comprising one or moreof: laser power of focal spot; focal spot width; focal spot centroidlocation; focal spot steering frequency; focal spot steering amplitude;focal spot steering angle; and focal spot polarization.
 6. The additivemanufacturing system of claim 1, further comprising a beam splitter thatredirects a portion of the set of laser beams to an optical imagingmodule, the optical imaging module comprising: a conjugate image formingoptic, one or more beam splitters, and a photo sensor comprising one ormore of a photo-array sensor and a pinhole photo-detector, wherein theoptical imaging module is configured to produce a conjugate image of aset of focal spots of the set of laser beams, and determine a set offocal spot characteristics of the set of focal spots to be used for beamshaping, wherein the photo sensor is located in the plane that isconjugated in respect to the plane of the set of focal spots at thematerial, and wherein the one or more controllers are configured tocontrol the set of focal spot characteristics during the performance ofeach beam shaping method.
 7. The additive manufacturing system of claim1, wherein the set of beam shaping methods comprises one or more of:coherent combining of a set of focal spots of the transmitted beams atthe material; incoherent combining of a set of focal spots of thetransmitted beams at the material; positioning of individual focal spotcentroids; controllable randomization of piston phases of a set oftransmitted beams; setting polarization states of the set of transmittedbeams; stair-mode scanning of coherently combined set of focal spots ofthe transmitted beams; scanning of all or a set of beam focal spots; andtime-multiplexing of sets of the above beam shaping methods.
 8. Theadditive manufacturing system of claim 7, wherein the beam shapingmethod comprises a set of laser power spatial distributionconfigurations selected to improve the manufacturing process and qualityof the target object, the set of laser power spatial distributionconfigurations comprising one or more of: focal spots of multiple beamspositioned in a line with a pre-selected power level for each beam alongthe line; focal spots of multiple beams positioned in a two-dimensionalpattern; a one dimensional or two-dimensional pattern of laser powerdistribution produced by scanned focal spots of a single or a set or allmultiple beams; and a one-dimensional or two-dimensional pattern oflaser power distribution produced by time-multiplexing of two or more ofthe set of beam shaping methods.
 9. The additive manufacturing system ofclaim 1, wherein the laser transmitter module further comprises one ormore laser receivers, and wherein the laser transmitter module isoperable as one or more laser transceivers.
 10. The additivemanufacturing system of claim 1, wherein the laser transmitter modulefurther comprises a set of beam forming optics comprising a virtual lensassembly, the virtual lens assembly comprising a set of beam formingoptical systems, wherein each beam forming optical system is configuredto independently focus a beam at a focal spot at the material, whereinthe set of beam forming optics is operable to focus a single beam or aset of collimated laser beams that are transmitted by the lasertransmitter module to provide overlapping of two or more focal spots atthe material.
 11. A method for additive manufacturing comprising thesteps: placing a material at a manufacturing surface of an additivemanufacturing system, the additive manufacturing system comprising alaser transmitter module operable to produce a set of laser beams toheat the material, the laser transmitter module comprising: a fiberarray laser head comprising a set of fiber-based laser transmitters, anda multi-channel optical power amplifier system comprising one or morecontrollers, the multi-channel optical power amplifier system operableto provide power to each of the set of fiber-based laser transmitters,and to provide control signals to generate and modify spatiotemporallaser power distribution formed by the set of laser beams at thematerial; providing a target object definition to a beam rasteringcontroller of the additive manufacturing system, the target objectdefinition comprising a set of coordinates defining a target object,wherein a beam shaping method selected from a set of beam shapingmethods is associated with each coordinate of the set of coordinates,wherein the beam rastering controller is communicatively coupled withthe laser transmitter module and a beam rastering system, wherein thebeam rastering system is operable to position the set of laser beamsrelative to the target object; at the beam rastering controller,determining a preconfigured instruction set based upon the target objectdefinition and providing a first portion of the preconfiguredinstruction set to the laser transmitter module and a second portion ofthe preconfigured instruction set to the beam rastering system; andbased on the preconfigured instruction and for at least one coordinateof the set of coordinates, causing the beam rastering system to positionthe set of laser beams and causing the laser transmitter module toperform the beam shaping method.
 12. The method of claim 11, wherein thelaser transmitter module further comprises: a set of sensors comprisingone or more of: a set of beam sensing modules, and a set of materialsensing modules; and a set of beam forming optics operable to modify oneor more of the set of laser beams, characterization of the material, andcontrol of an additive manufacturing process based upon the output ofthe set of sensors; the method further comprising the steps of:receiving a set of sensor data from the set of sensors; determining adynamic instruction set based upon the target object definition and theset of sensor data, the dynamic instruction set comprising a dynamicinstruction set for a beam shaping method that is selected to improvethe manufacturing process and quality of the target object; andproviding a first portion of the dynamic instruction set to the beamrastering controller; wherein the dynamic instruction set is configured,for at least one coordinate of the set of coordinates, to guide the beamrastering system to position the set of laser beams and cause a dynamicbeam shaping method to be performed based upon the dynamic instructionset for a beam shaping method.
 13. The method of claim 12, wherein theset of material sensing modules comprises one or more of: amanufacturing surface sensor comprising a first probe beam laserilluminator and a first optical receiver, configured to provide a firstprobe beam oriented and focused to precede a path of the set of beamsand operable to determine characteristics of a powder material prior toa molten pool stage along a processing track; a molten pool sensorcomprising a second probe beam laser illuminator and a second opticalreceiver, configured to provide a second probe beam oriented and focusedat the molten pool area and operable to determine characteristics of amolten pool; and a processed track sensor comprising a third probe beamlaser illuminator and a third optical receiver, configured to provide athird probe beam oriented and focused to follow a path of the set oflaser beams behind of the molten pool and operable to determinecharacteristics of a processed track.
 14. The method of claim 12,wherein the additive manufacturing system further comprises a beamsplitter that redirects a portion of the set of laser beams to anoptical imaging module, the optical imaging module comprising: aconjugate image forming optic, one or more beam splitters, and a photosensor comprising one or more of a photo-array sensor and a pinholephoto-detector, wherein the optical imaging module is configured toproduce a conjugate image of a set of focal spots of the set of laserbeams, and determine a set of focal spot characteristics of the set offocal spots to be used for beam shaping, and wherein the photo sensor islocated in the plane that is conjugated in respect to the plane of theset of focal spots at the material, further comprising the step of,using the one or more controllers, controlling the set of focal spotcharacteristics during the performance of each beam shaping method. 15.The method of claim 12, wherein the set of beam shaping methodscomprises one or more of: coherent combining of a set of focal spots ofthe transmitted beams at the material; incoherent combining of a set offocal spots of the transmitted beams at the material; positioning ofindividual focal spot centroids; controllable randomization of pistonphases of a set of transmitted beams; setting polarization states of theset of transmitted beams; stair-mode scanning of coherently combined setof focal spots of the transmitted beams; scanning of all or a set ofbeam focal spots; and time-multiplexing of sets of the above beamshaping methods.
 16. The method of claim 15, wherein the beam shapingmethod comprises a set of laser power spatial distributionconfigurations selected to improve the manufacturing process and qualityof the target object, the set of laser power spatial distributionconfigurations comprising one or more of: focal spots of multiple beamspositioned in a line with a pre-selected power level for each beam alongthe line; focal spots of multiple beams positioned in a two-dimensionalpattern; a one dimensional or two-dimensional pattern of laser powerdistribution produced by scanned focal spots of a single or a set or allmultiple beams; and a one-dimensional or two-dimensional pattern oflaser power distribution produced by time-multiplexing of two or more ofthe set of beam shaping methods.
 17. The method of claim 12, wherein thelaser transmitter module further comprises one or more laser receivers,and wherein the laser transmitter module is operable as one or morelaser transceivers.
 18. The method of claim 12, wherein the lasertransmitter module further comprises a set of beam forming opticscomprising a virtual lens assembly, the virtual lens assembly comprisinga set of beam forming optical systems, wherein each beam forming opticalsystem is configured to independently focus a beam at a focal spot atthe material, wherein the set of beam forming optics is operable tofocus a single beam or a set of collimated laser beams that aretransmitted by the laser transmitter module to provide overlapping oftwo or more focal spots centroid at the material.
 19. An additivemanufacturing system comprising: a manufacturing surface comprising amaterial and a target object; a laser transmitter module operable toproduce a set of laser beams to heat the material, comprising: a fiberarray laser head comprising a set of fiber-based laser transmitters, amulti-channel optical power amplifier system comprising one or morecontrollers, the multi-channel optical power amplifier system operableto provide power to each of the set of fiber-based laser transmitters,and to provide control signals to generate and modify spatiotemporallaser power distribution formed by the set of laser beams at thematerial, a set of sensors comprising a set of beam sensing modules anda set of material sensing modules, a set of beam forming optics operableto modify one or more of the set of beams, characterization of thematerial, and control of an additive manufacturing process based uponthe output of the set of sensors; a beam rastering system operable toposition the set of laser beams relative to the target object; a beamrastering controller, wherein the beam rastering controller iscommunicatively coupled with the laser transmitter module and the beamrastering system; wherein the beam rastering controller is configuredto: receive a target object definition, the target object definitioncomprising a set of coordinates defining the target object, wherein abeam shaping method selected from a set of beam shaping methods isassociated with each coordinate of the set of coordinates; determine apreconfigured instruction set based upon the target object definitionand provide a first portion of the preconfigured instruction set to thelaser transmitter module and a second portion of the preconfiguredinstruction set to the beam rastering system; and based on thepreconfigured instruction set and for at least one coordinate of the setof coordinates, cause the beam rastering system to position the set oflaser beams and cause the laser transmitter module to perform the beamshaping method; and wherein the one or more controllers are configuredto: receive a set of sensor data from the set of sensors; determine adynamic instruction set based upon the target object definition and theset of sensor data, the dynamic instruction set comprising a dynamicinstruction set for a beam shaping method that is selected to improvethe manufacturing process and quality of the target object; and providea first portion of the dynamic instruction set to the beam rasteringcontroller; wherein the dynamic instruction set is configured, for atleast one coordinate of the set of coordinates, to guide the beamrastering system to position the set of laser beams and cause a dynamicbeam shaping method to be performed based upon the dynamic instructionsset for a beam shaping method.